- The wide use of particulate materials in industry has elicited various problems that are related to particle size variations (increase or decrease) in diverse mechanical processes. One of the main problems is the low accuracy of designing size reduction systems. The particles break as a result of continuous loads higher than their strength. The particles may also break due to repeated loads lower than their strength (a phenomenon related to fatigue). Therefore, a characterization of particle strength with static and repeated loads is crucial. The current work introduces and validates the fatigue model which development is based on the theoretical model. The modified model enables us to calculate particle strength decreases with every additional loading event. The model depends on six empirical and material related parameters, and was validated by appropriate experiments with a variety of NaCl particle sizes. Since the fatigue effect among particulate materials is a very common event, this study may enable the simulating comminution processes with higher accuracy.